// Copyright 2016 The Draco Authors.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//      http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//
#ifndef DRACO_COMPRESSION_ATTRIBUTES_PREDICTION_SCHEMES_PREDICTION_SCHEME_ENCODING_TRANSFORM_H_
#define DRACO_COMPRESSION_ATTRIBUTES_PREDICTION_SCHEMES_PREDICTION_SCHEME_ENCODING_TRANSFORM_H_

#include "draco/compression/config/compression_shared.h"
#include "draco/core/encoder_buffer.h"

namespace draco {

// PredictionSchemeEncodingTransform is used to transform predicted values into
// correction values.
// CorrTypeT is the data type used for storing corrected values. It allows
// transforms to store corrections into a different type or format compared to
// the predicted data.
template <typename DataTypeT, typename CorrTypeT>
class PredictionSchemeEncodingTransform {
  public:
    typedef CorrTypeT CorrType;
    PredictionSchemeEncodingTransform() : num_components_(0) {}

    PredictionSchemeTransformType GetType() const {
        return PREDICTION_TRANSFORM_DELTA;
    }

    // Performs any custom initialization of the transform for the encoder.
    // |size| = total number of values in |orig_data| (i.e., number of entries *
    // number of components).
    void Initialize(const DataTypeT * /* orig_data */, int /* size */,
                    int num_components) {
        num_components_ = num_components;
    }

    // Computes the corrections based on the input original values and the
    // predicted values. The correction is always computed for all components
    // of the input element. |val_id| is the id of the input value
    // (i.e., element_id * num_components). The default implementation is equal to
    // std::minus.
    inline void ComputeCorrection(const DataTypeT *original_vals,
                                  const DataTypeT *predicted_vals,
                                  CorrTypeT *out_corr_vals) {
        static_assert(std::is_same<DataTypeT, CorrTypeT>::value,
                      "For the default prediction transform, correction and input "
                      "data must be of the same type.");
        for (int i = 0; i < num_components_; ++i) {
            out_corr_vals[i] = original_vals[i] - predicted_vals[i];
        }
    }

    // Encode any transform specific data.
    bool EncodeTransformData(EncoderBuffer * /* buffer */) {
        return true;
    }

    // Should return true if all corrected values are guaranteed to be positive.
    bool AreCorrectionsPositive() const {
        return false;
    }

  protected:
    int num_components() const {
        return num_components_;
    }

  private:
    int num_components_;
};

}  // namespace draco

#endif  // DRACO_COMPRESSION_ATTRIBUTES_PREDICTION_SCHEMES_PREDICTION_SCHEME_ENCODING_TRANSFORM_H_
